I have written a RPG called "Chuť magie" - it's in Czech and it means literary "Taste of Magic", but I'd definitely call it "High on Magic" in English. I'm not planning to translate it to English soon, unless paid for it significantly, but I'm curious how original is it :-)

There are other alternative and quite original features (no GM for example), but I'm asking about originality of the magic system, where magic is limited by making the mage PC do weird or funny things, which have in-game consequences (they are not just flavour)? The PC can be forced to do such things either directly ("you must...") or indirectly ("you are penalized, but you can do XY to erase the penalty" - this is what I use there). Do you know about such a system (or subsystem for magic within more general game)? Or, ideally, list of such systems as complete as possible?

EDIT to clarify things:
Mage can do almost anything, limited by complexity of the spell, his magical abilities and level of "tipsiness", the measure how he's "high" on magic. The more complex the spell, the lower the chance of casting and the more tipsiness the mage gets. Tipsiness work as a universal penalty, but it can be decreased by doing non-magical hobbies (important trait of a PC - these can be normal or strange, but should make conflicts with other characters, because the system encourage it) or playing symptoms of magical intoxication, like casting spells the mage has almost no chance to cast succesfully or do other (almost) impossible things, insult others, break things etc. Any player can trigger this, but the PC's player can increase his tipsiness and get a saving roll. These strange things usually have some consequences, they are not just consmetic effect.
This is where my original formulation was bad - it didn't exclude "just flavour" effects, which are nice, but not exactly what I wanted.

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There's a couple of things that may need clarifying if you want some better answers. Are you handing out the choice of things that have to be done, rolling them on a table or agreeing them with the players?
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Simon GillNov 24 '12 at 22:44

@SimonGill The way I read the question, Pavel uses a system where the player is able to take (negative) consequences to remove a penalty given out for magic.
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DakeyrasNov 24 '12 at 23:47

It's been said that there are no original ideas in RPGs, just original combinations. This sounds, in its totality, unlike any other RPG I've heard of. I would say you don't need to worry about originality. :)
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SevenSidedDieNov 25 '12 at 20:01

While only tangentially similar, Lyrium was supposed to be addictive in Dragon Age and Lyrium was the substance that provided magical energy. I can't think of anything precisely the same.
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TimothyAWisemanJan 5 '13 at 1:51

4 Answers
4

Sounds to me like the Bunk system from Changeling: The Dreaming. The difficulties for casting spells (called cantrips) are fairly high, but they're lowered by the performance of fairly bizarre or outlandish tricks. (Reciting the alphabet backwards; smoking an entire pack of cigarettes at one time; leading the group in a sing-along; so on.)

where the players are mages, some of the factions have strange addictions to magic, and there is even a mechanic for the drawbacks that magic can have on players who use it too much. Paradox from the site:

Paradox is accrued when a Mage uses vulgar magic that cannot be
explained by Sleeper's idea of what Reality is and what laws govern
it. Effects such as crushing a car with your bare hands are vulgar and
will gain you paradox. However, it is possible to bypass paradox
through the use of coincidental magic by aligning the Effect with the
rules of consensual reality (the overall beliefs of the sleepers). The
same effect of destroying the car could be coincidentally performed by
manipulating a street light to fall on the car. If the offending mage
has acquired a significant amount (6 or more points) of Paradox, they
may experience what is known as Backlash.

Backlash can occur in one of four ways; Either the mage acquires
direct damage (amount and type depends on the amount of Paradox
accrued), the mage becomes the target of a malicious Paradox Spirit,
the mage may acquire Paradox Flaws (explained below), or the mage and
those nearby can be sucked into a Paradox Realm in the same vein as
the magic in question. (Correspondence could create a spatial loop,
Time could create the repetition of certain hours or days.) Some
certain objective would have to be achieved in order to escape from
the infinite loop.

Paradox Flaws are very curious events that may occur for a limited or
permanent duration in the presence of a mage who has suffered Paradox
Backlash. They can be as trivial as a watch running in reverse or
shadows falling in the wrong direction, right handed people becoming
left handed, images in mirrors doing different things than their
counterparts in the real world, hearing things before they are said,
needing dark instead of light to see, or perhaps missing or altered
memories. They can be trivial (the mage's watch running backward at
high speed for a few turns or flowers wilting nearby), minor (the
mage's feet sticking to the ground for a turn or an uncontrollable
sneezing attack), moderate (suddenly exuding waves of heat or cold,
losing the ability to speak coherantly), severe (facial features
vanish but senses remain, all cloth items within five feet start
writhing), or drastic (skin turns to wood and starts sprouting,
unintentionally firing off attacks at friends, a permanent minor
flaw).

"Paradox is a fickle force. Sometimes it backlashes; sometimes it
waits. Sometimes it's a hammer and sometimes it's like sandpaper
against your skin.

Paradox usually ignites as it's garnered, but not always. Figure about
a one-in-ten chance that Paradox will hang on a mage instead of
backlashing immediately. And, of course, the player can always spend
Willpower to prevent the Paradox from going off all at once.
Ultimately it's up to the Storyteller to decide whether the Paradox
explodes as gathered or whether it hangs in the balance." (from WW's
Mage-FAQ)

The two simple presumptions are expressed in the Blood Elves of World of Warcraft. That is a setting detail which isn't exactly emphasised during play in the online game or the tabletop versions.

The magic system sounds roughly familiar to one of the aspects of the Dresden Files RPG. Two of the options to gather the power to cast a Thaumaturgic spell are making declarations and taking consequences. Evocation generates mental stress, which can quickly turn into consequences.

As a narrative system, players and the storyteller make the declaration or take the consequence up front mechanically but narratively it could take effect afterwards. This gives the players some control over the strangeness that occurs.

This system could be easily reskinned by moving all magic to an addiction stress track and limiting the number of declarations that can be made. Now any spell of significance requires the caster to generate penalties for himself that are relevant to magical weirdness.

There is some more detail about DF Thaumaturgy out there. Look under the Make Declarations and Take Consequences point in the Preparation Phase section.

Forcing people to pay a price isn't a new idea. There can of course be new takes on it and I think this is one based on the level and kinds of effects that you expect to give people.

It's not exactly what I have in my systems (a declaration is something you do before casting X in my game magic makes you do strange things after you cast spell), but definitely a good try, and something new to me. +1, but I'm not considering accepting the answer.
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PavelNov 24 '12 at 22:30

I've certainly not encountered anything precisely the same. As already mentioned in some of the previous answers, there are a number of magic systems out there where magic can be addictive or has drawbacks (Mage from WW being the closest example I can think of).

It's hard to be sure quite how close things are likely to be to what's already out there without having a good long look at the system and I'm afraid my mastery of Czech is non-existent. However, it sounds like you have something that is likely to be more extreme in its price for magic than the vast majority of systems out there and I suspect, from what you've said about the system, that it's unique at least at the level of the mechanics and the extremity of price for using magic.